86 Monte Carlo SS brake booster, can I replace with a universal fit or not?

My 86 monte has a 9" dual (I think based on the thickness) brake booster mounted directly to the firewall. I dont think theres a bracket. It works fine but I want to replace it with a stainless (preferred) or chrome booster. I know that MBM makes some but none seem a direct fit according to where I see them being sold

Anyone know if I can just put a universal one in? Maybe drill the firewall a bit? Or is there more too it than just getting it mounted?

I dont know the bolt distances on the original because its in a running car and want to do a weekend swap if possible. I'll be doing the master as well and a new proportioning valve, probably new lines